Yes Mr Bean it is a missile that travels from the cater towards the target(s).
Amount of HP healed cannot be greater than the max HP of the caster (meaning if the caster has 100 HP max he cannot become 105 or more because of this spell, even if the damage done is more than the amount that has to be healed)
Ex.1: DeathKinght(DK) has 40/100 HP - two enemy Grunts near by both have 15/100 HP, after they got hit by the spell (they die - damage dealt 2x15) amount healed to the DK = 30 becomes 70/100
Ex.2: DeathKinght(DK) has 40/100 HP - two enemy Grunts near by both have 45/100 HP, after they got hit by the spell (they die - damage dealt 2x45) amount healed to the DK = 60 becomes 100/100 HP